The present invention relates to a magnetic head for use with a magnetic disk drive.
Since magnetic disk drives are high-reliability, large-capacity storage devices, they are widely used in the field of storage, which is essential to the present-day information technology society. The amount of information handled in the information technology society is strikingly increasing. As a matter of course, it is therefore demanded that the magnetic disk drives improve their performance to process a large amount of information within a short period of time.
FIG. 2 illustrates a magnetic head that is installed in a magnetic disk drive. A suspension 8 applies load as needed to press the magnetic head 1 against the surface of a recording medium 2. The suspension 8 is supported by an arm 7 and transmits the motion of a rotary actuator 4 to the magnetic head. When the rotary actuator 4 rotates, the magnetic head 1 moves over the surface of the recording medium 2, accomplishes positioning at a certain location, and then writes or reads magnetic information. In this instance, the write/read process for the magnetic head 1 is performed by a preamplifier circuit 6. The recording medium 2 is rotated by a motor 3. The electric circuitry for controlling the above operations exists together with a signal processing circuit 5.
As shown in FIG. 3, the magnetic head comprises an information write function section 10 and a read function section 11. The write function section 10 comprises a coil 12, a lower core 15, an upper core 14, a magnetic body 36, and a pedestal magnetic pole piece 28. The lower and upper cores are positioned so as to enclose the coil. The rear end of the magnetic body is magnetically coupled to these cores. The pedestal magnetic pole piece is positioned on an air bearing surface 30 (x-z plane). The track width is prescribed by the width of the upper core's protrusion through the air bearing surface 30.
A magnetic gap 29 is provided between the pedestal magnetic pole piece 28 and upper core. Magnetic field leakage from the magnetic gap is used to write magnetic information onto the recording medium.
The read function section 11 comprises a magnetoresistive device 19 and an electrode 20, which causes a constant current flow to the magnetoresistive device and detects a resistance change. An upper magnetic shield 17 and a lower magnetic shield 18 are positioned so as to enclose the magnetoresistive device 19 and electrode 20. These magnetic shields are used to shield against an unnecessary magnetic field during replay. These functionality units are formed on a magnetic head main body 25 via a nonmagnetic, insulative underlying layer 26.
The read function section illustrated in FIG. 3 is of a type that allows a sense current for detecting magnetic information to flow in a plane parallel to shields 17, 18. A read function section that incorporates both the shields and electrode has been commercialized in recent years. This new type of read function section causes a sense current flow to the magnetoresistive device in the direction of the film thickness. It is called a CPP (current perpendicular to plane) type device because its current flow is perpendicular to the film. Even when this type of device is used, no limitation is imposed on the write function section including a lower magnetic pole piece 15.
It is common in recent years that a step 31 is formed as shown in FIG. 3 by selectively etching the surface of the pedestal magnetic pole piece 28 using the upper core 14 protruding through the air bearing surface 30 as a mask. The ion milling method is generally used for step formation.
Further, a method for effectively decreasing the depth of the write gap (gap depth) by removing the rear end surface of the pedestal magnetic pole piece by means of etching (or by forming a magnetic film on the air bearing surface side) is effective in obtaining a strong magnetic field.
The basic structure of the head containing the pedestal magnetic pole piece described above is disclosed in U.S. Pat. No. 6,417,990. This structure entails a process for forming the upper core 14 in a plane after covering the rear end area including the pedestal magnetic pole piece with a nonmagnetic film. The process is employed in order to form a narrow track section with high precision when the upper core is formed later (it is obvious that a stepped part is likely to incur a resolution failure at the time of exposure).
For magnetic disk drive density increase, it is demanded that the magnetic head increase the magnetic field gradient and provide a uniform magnetic field in the direction of the recording track width. To meet such a demand, it is important that a highly saturated magnetic material be used as the magnetic pole material and that the write gap be narrowed (to decrease the distance between the lower magnetic pole piece and track-width-determining magnetic pole piece).